[Responses of neurons of the first and second somatosensory zones of the cortex to peripheral, thalamic and cortical stimulation].

Experiments were performed on cats immobilized with d-tubocurarine or myorelaxin. Neuronal responses were studied in the first somatosensory cortex (SI) to the second somatosensory cortex (SII), ventroposterior nucleus (VP) and contralateral forepaw stimulation. Besides, neuronal responses in SII to SI, VP and contralateral forepaw stimulation were also studied. It was shown that in SII the percentage of neurons excited by afferent volley with two or more synaptic change-overs in the cerebral cortex was larger than in SI. Neurons of SI and SII responded to cortical stimulation ortho- and antidromically, thus confirming the existence of bilateral cortico-cortical connections. Both in SI and SII, PSPs to cortical stimulation were similar in character to PSPs in the same neurons to VP stimulation. In 50.0% of SI neurons and 37.1 of SII neurons the difference in latencies of orthodromic spike potentials to VP and cortical stimulation was less than 1.0 ms. In 19.6% of SI neurons and 41.4% of SII neurons the latency of the response to cortical stimulation was 1.6-4.7 ms shorter than that of the response in the same neuron to VP stimulation. It is supposed that impulses from SI participate significantly in afferent activation of SII neurons.